1. Field of the Invention
The present invention relates to highly processable aromatic polyamide fibers, their production and use.
Due to recent demands, various novel high strength, high modulus fibers, such as aromatic polyamide (aramid) materials, have been proposed to reinforce elastomeric and plastic materials.
2. Description of the Prior Art
U.S. Pat. No. 3,869,429 and its German equivalent DE 22 19 703 as well as U.S. Pat. No. 3,287,324 describe aromatic polyamides and wholly aromatic polyamides useful for making fibers and films for various applications.
U.S. Pat. No. 4,670,343 is related to a wholly aromatic polyamide fiber which has improved surface frictional characteristics, especially to a wholly aromatic fiber which exhibits a reduced filament-to-filament friction, low breakage and fibrillation and a high strength, which is used in a twisted form as a reinforcing cord for rubber or composite materials. The fiber is coated with at least 0.05% by weight of a reaction product, of a polyoxyethylene adduct of glyceride having at least one hydroxyl group in the molecule with a dibasic acid and/or a dibasic anhydride. The fiber itself is cured and drawn at 500.degree. C.
EP 0 107 887 relates to a multi-filament yarn which entirely or substantially consists of an aromatic polyamide which is provided with an adhesive coating of a cured epoxy compound. The epoxy compound having an average of 2 to 4 epoxy groups per molecule is applied to the yarn as an aqueous solution or dispersion. After being taken up by the yarn, the epoxy compound is cured at temperatures between 220.degree. C. and 230.degree. C. which results in the formation of a coating being present on the yarn in between 0.01 and 5% by weight. The epoxy compound, curing agent and catalyst containing solution may be applied to the freshly spun wet filament or to the dried filament.
EP 0 136 727 describes the preparation of an aromatic polyamide filament yarn which is impregnated with solid particles of a fluorine containing polymer (PTFE) and/or graphite from an aqueous dispersion. The yarn is then subjected to a blowing treatment while in the wet state.
EP 0 239 915 is related to a process for producing a modified fibrous material from aromatic polyamide fibers by applying a cold plasma treatment under reduced pressure to the surface of the fiber in order to achieve an enhancement of the bonding property of the fiber to rubber. To this fiber an ion-plating treatment with a polyamide vapor is applied under reduced pressure. After impregnating the fiber with an adhesive composition, the product is then dried and cured at elevated pressure.
In the state of the art of the above mentioned last 4 references a resin is applied to the fiber as impregnating agent in order to facilitate the reinforcement of rubber articles and other materials. After the application a curing step is always necessary in which the surface reacts with the resin.
Another reference (Research Disclosure, May 1978, No. 169, disclosure 16949) discloses finishes useful for treating industrial fibers, such as polyamide and copolyamide yarns, for tire cords which contain ingredients selected from
(a) natural or synthetic lubricant such as cocunut oil, palm oil, pentaerythritol tetrapelargonate or ditridecyl adipate,
(b) a nonionic emulsifier with a hydrophiliclipophilic balance (HLB) of 11-14, such as PEG (400-600) monostearate or mono-oleate, polyoxyethylene (30) sorbitol tetraoleat-monolaurate or polyoxyethylene (4) sorbitan monolaurate,
(c) a nonionic emulsifier with an HLB of 7-10, such as PEG (400) distearate or dioleate, polyoxyethylene (3) sorbinate monostearate, polyoxyethylene (40) septaoleate or polyoxyethylene (5) stearic acid,
(d) an antioxidant, such as tris-nonylphenyl phosphite, 4,4'-butylidene-bis-(6-t-butyl-m-cresol), tetra bis [methylene-3-(3',5'-di-t-butyl-4-hyrdoxy-phenyl)propionate]methane, or the product derived from condensation of butylated p-cresol and dicyclopentadiene,
(e) a substituted polysiloxane, such as dimethyl, diphenyl, methylethyl or methyl-phenyl polysiloxane, and
(f) a sulfonated natural oil, such as peanut or palm oil.
One preferred composition contains 60-70 parts (a), 15-25 parts (b), 5-15 parts (c) and 1-5 parts (d). Another contains 60-70 parts (a), 15-25 parts (b), 5-15 parts (c), 2-10 parts (d) and 1-7 parts (e). Another contains 55-65 parts (a), 15-25 parts (b), 5-15 parts (c), 1-5 parts (d), and 5-15 parts (f). Another contains 55-65 parts (a), 15-25 parts (b), 5-15 parts (c), 2-10 parts (d) 1-5 parts (e) and 5-15 parts (f). A still other reference (Research Disclosure, Jul. 1980, No. 195, disclosure 19520) discloses finishes useful for treating industrial fibers, such as polyamide and aramid fibers, which contain ingredients selected from
(a) natural or synthetic esters such as coconut oil, palm oil, pentaerythritol tetrapelargonate, ditridecyl adipate, or an interesterified combination of glycerol trioleate, coconut oil, and palm oil or tridecyl oleate,
(b) products derived by reacting a fatty acid or acids with an adduct of ethylene oxide and a polyol or with a polyethylene glycol compound such as polyoxyethylene (2-10) sorbitan monolaurate, polyoxyethylene (20-50) sorbitol septaoleate, polyoxyethylene (20-40) sorbitol tetraoleatemonolaurate, polyethylene glycol (400-600) monostearate or monolaurate or polyethylene glycol (400-600) dilaurate,
(c) an ethoxylated glyceride obtained from the reaction of 1 mole of castor oil, hydrogenated castor oil, or coconut oil with 10-50 moles of ethylene oxide,
(d) tris(nonylphenyl)phosphite, 4,4'-butylidene-bis(3-methyl-6-tert butylphenol), or 4,4'-thio-bis(3-methyl-6-tert butyl-phenol) and
(e) a biostat such as o-phenylphenol or the sodium or potassium salt of 2-pyridinethiol-1-oxide.
One preferred composition contains 60-70 parts (a), 20-40 parts (b), up to 5 parts (d), up to 5 parts (e), and up to 5 parts water. A second preferred composition contains 45-55 parts (a), 20-30 parts (b), 20-30 parts (c), up to 5 parts (d), up to 5 parts (e), and up to 5 parts water. When polyamide or aramid fibers bearing any of the above finishes are crimped, a compound from the group of
i) polyoxyethylene (20-40) sorbitan monostearate, PA1 ii) polyoxytheylene (15-30) sorbitan tristearate, PA1 iii) polyoxyethylene (15-30) sorbitan monooleate, or PA1 iv) the potassium or sodium of the product of the reaction of 1 mole of phosphorus pentoxide and 2-3 moles of a fatty alcohol such as lauryl alcohol, hexadecyl alcohol, or stearyl alcohol
is advantageously applied at the crimper. Staple prepared from the fibers treated as described above is advantageously treated with IV), above, after crimping and prior to further processing.
In the two last cited references, finishes are disclosed which contain a lubricant, comprised of esters composed of an aliphatic, saturated carboxylic acid and a polyhydric or aliphatic unbranched alcohol. These finishes also contain an emulsifier or emulsifying system, an antioxidant to increase the stability of the composition, polysiloxanes as further thermostable lubricant, a sulfated natural oil as antistatic agent which is, however, not hydrolysis-stable. Furthermore, these finished may contain biostats, further emulsifiers or lubricants.
However, the finishes according to these references are not suitable for the purposes of the present invention in terms of surface frictional properties, scourability, depositing due to abrasion, fibrillation and antistatic properties of the resulting treated fibers.
Most of the commercial products have a high rigidity, poor surface functional characteristics leading to fibrillation, mainly caused by friction among filaments, and poor surface affinity for most traditional elastomeric, thermoplastic and thermoset matrices which they reinforce.